Hi!  This error seems to occur randomly, seen on riscv64:

https://ci.debian.net/packages/s/snowflake/testing/riscv64/71982807/#L2681

818s --- FAIL: TestQueuePacketConnWriteToKCP (5.80s)
818s panic: empty transcript [recovered, repanicked]
818s
818s goroutine 33 [running]:
818s testing.tRunner.func1.2({0x1abcc0, 0x2133f0})
818s 	/usr/lib/go-1.26/src/testing/testing.go:1974 +0x168
818s testing.tRunner.func1()
818s 	/usr/lib/go-1.26/src/testing/testing.go:1977 +0x242
818s panic({0x1abcc0?, 0x2133f0?})
818s 	/usr/lib/go-1.26/src/runtime/panic.go:860 +0x104
818s gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/turbotunnel.TestQueuePacketConnWriteToKCP(0x2335681fcb48)
818s 	/tmp/autopkgtest-lxc.ve3aic5v/downtmp/autopkgtest_tmp/_build/src/gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/turbotunnel/queuepacketconn_test.go:221 +0x316
818s testing.tRunner(0x2335681fcb48, 0x210e88)
818s 	/usr/lib/go-1.26/src/testing/testing.go:2036 +0xc4
818s created by testing.(*T).Run in goroutine 1
818s 	/usr/lib/go-1.26/src/testing/testing.go:2101 +0x38a
818s FAIL gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake/v2/common/turbotunnel 6.512s

/Simon

Hi.  This has been seen again, with a slightly different error message.
Still flaky, it often succeeds.

https://ci.debian.net/packages/s/snowflake/testing/arm64/73803920/#L2753

299s === RUN   TestQueuePacketConnWriteToKCP
299s     queuepacketconn_test.go:231: 8 1 packet changed between send and recv
299s         send: "\xd4%\x89\x81Q\x00 \x00|\x11\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\v\x00\x00\x00hello world"
299s         recv: "\U000906efQ\x00 \x00\x94\x0e\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\v\x00\x00\x00hello world"
299s --- FAIL: TestQueuePacketConnWriteToKCP (4.67s)

/Simon